BOSTON -- Felix Doubront was throwing 88-mph fastballs in the fifth inning of the Boston Red Sox's game against the Toronto Blue Jays on Tuesday night before his shoulder went numb.

It was nothing like he ever felt before.

He had averaged about 92 mph on his fastball before Tuesday. Fatigue is no stranger to Doubront, who has suffered similar ailments in the past, but typically not until August or September. And numbness -- this was new.

Pitching with a tired shoulder, Doubront was lit up by the power-hitting Blue Jays for five runs on two homers as the Red Sox dropped their fifth straight, this one by a score of 7-4.

The good news: Doubront said he was feeling fine after the game. He'll go for an MRI on Wednesday morning to get definitive results.

"Just wait to tomorrow to see what kind of tightness is there," he said. "I felt fine during the game. Right now I feel fine. During the game, I couldn't feel my shoulder. Weird."

Perhaps the Red Sox were demoralized after making two comebacks on the Minnesota Twins last week and losing both on walk-off hits against Andrew Miller. They tied last Tuesday's game, 6-6, before losing in the ninth. Two days later, they again tied it late to lose in the 10th inning. They've lost six of their last seven.

Doubront's injury-plagued outing comes after he made three straight quality starts, holding opponents to a .246 average as the Red Sox went 2-1 with Doubront on the mound. The Blue Jays, who lead the American League in home runs, didn't need any help.

Edwin Encarnacion labeled a two-run shot high into the Boston skyline and well over the Green Monster to give Toronto a 2-0 lead.

Allowing a home run to Encarnacion isn't rare. Allowing one to 33-year-old journeyman catcher Erik Kratz is. Kratz took Doubront deep to center field in the fourth inning.

Doubront allowed a pair of well-struck doubles to start the fifth before he received a mound visit from Red Sox manager John Farrell. Shortly after Farrell arrived the skipper signaled for the trainers to join him and Doubront was removed from the game.

"A couple of the hits, he threw an 85-mile-an-hour heater, and I know that's not him," said catcher David Ross. "He was kind of cutting his fastball all day, which tells me he wasn't trusting the release."

Doubront threw just 65 pitches and allowed five runs.

"When he came out in the fifth inning, it was clear the overall power to the stuff started to diminish," said manager John Farrell. "He felt some restriction in the shoulder where he was not able to generate normal arm speed."

Should Doubront miss a start, the Red Sox could turn to Chris Capuano, was signed to be a sixth starter but has flourished as a left-handed reliever. Brandon Workman, Anthony Ranaudo, Matt Barnes and Allen Webster linger at Triple-A Pawtucket. Workman is scheduled to start Thursday but could be held back in case the Red Sox choose to recall him. Ranaudo's turn in the rotation comes Sunday, when Doubront's next turn would be up with the Red Sox.

With news of the Red Sox's agreement to bring back free agent shortstop Stephen Drew still fresh in the Fenway Park air, 21-year-old shortstop Xander Bogaerts made a high throw that sailed away for an error on the second play of the game. In the fifth inning, he made another error, this time dropping a ball he had originally fielded cleanly in his glove.

"I mean, there was a lot going on today," Bogaerts said. "I don't want to make no excuses, but it was definitely a tough day."

Bogaerts had a chance to redeem himself with bases loaded and one out in the fourth inning, but luck wasn't on his side. He roped a line drive to the third baseman, Brett Lawrie, who dropped it, then stepped on third and threw home for a double play. Bogaerts later singled and walked to raise his on-base percentage to .372.

Doubles from Brock Holt, Jackie Bradley Jr. and Dustin Pedroia added two runs in the fifth, when the Red Sox cut Toronto's lead to 6-2. Given a chance with runners on first and second and nobody out later in the game, Holt was ordered to sacrifice bunt. Nobody scored in the inning.

"We're looking to anything we can to scratch out a run," Farrell said.

The Red Sox didn't have enough to make up for Doubront's poor outing.

Doubront's strikeout rate and groundball rate have been at three-year lows this season.

The Red Sox already made one reactionary change, agreeing to a contract with Drew before the calendar turns to June.